The combination of X-ray-irradiation-induced photochromism and persistent radioluminescence in a single material presents an exciting avenue for multi-functional applications such as optical memory, anti-counterfeiting, and X-ray detection and imaging. However, developing such a material remains a significant challenge. Here, a white Ba3MgSi2O8:Mn2+ photochromic phosphor was prepared, exhibiting a white-to-orange color change (>20 h for bright field) and good persistent radioluminescence emission (>90 min for dark field) in response to X-ray radiation. The photochromic phosphor also demonstrated accelerated bleaching and recovery after 14 min of 254 nm UV light stimulation. This Ba3MgSi2O8:Mn2+-based flexible film displayed simultaneous reversible photochromism and recoverable persistent luminescence, providing dual-mode X-ray imaging and detection capabilities, as well as good reproducibility and read/write erasability. This study suggests that combining X-ray-induced photochromism and persistent radioluminescence in a single material is a promising approach to design advanced photonic materials for information security, cryptography, and smart anti-counterfeiting applications.

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Double perovskite (DP) phosphors attract extensive attention due to their potential applications in the field of optoelectronics. Photochromism‐induced luminescence modulation can extend their application fields. However, designing and preparing DP phosphors with expected photochromic and luminescent properties is still challenging. Herein, the photochromic Ba2YTaO6: Yb3+, Er3+, Co2+ DP with upconversion luminescence properties is developed. The color of the sample turns from white to pink upon 254 nm UV light irradiation, which is fast fading upon 473 nm laser illumination. The mechanism of photochromism is related to the formation of color centers, and the doping of Co2+ ions is crucial for the improvement of photochromism, which is from the increasing of traps depth, the oxygen vacancies, and the carrier concentration of the matrix caused by Co2+ doping. The upconversion luminescence of Er3+ ions can be reversibly modulated by the photochromic effect, exhibiting excellent reproducibility and high stability. The potential application of photochromic Ba2YTaO6: Yb3+, Er3+, Co2+ phosphor is demonstrated in the field of anticounterfeiting and three‐dimensional (3D) artwork. This work not only offers insight into the photochromic mechanism of DP but also presents guidance for developing other photochromic DP phosphors.